How did Bin Laden and al-Qaeda attempt to appeal to Muslims worldwide?

Answer 1

Most Muslims are Peaceful
Before we discuss the appeal of Jihadism, we should note that most Muslims are peaceful. Islamic terrorism is a very small percentage of the Muslim population, just as terrorists in general are a minimal part of the population. Terrorists make up less than 1% of Muslims (it is estimated that there are roughly 300,000 Jihadists in the world out of 1.6 billion Muslims). The reason that this <1% of Muslims are so infamous is that Jihadists are responsible for an inordinate share of casualties. In the last ten years, over 85% of terrorist incidents and 85% terrorist-related fatalities were perpetrated by Muslims.

Introduction
Now that we have our disclaimer that we are talking about a minority of the worldwide Muslim community, we can actually discuss the appeal that Jihadism has. Jihadism is the idea that (1) national laws should be based on the Shari'a or Islamic Law and (2) the imposition of Islamic Law should be done using violence or military force (as opposed to democratically). Jihadism is the ideology that motivates al-Qaeda (and Bin Laden), Boko Haram, Islamic State (ISIL), AQIM, Hezbollah, Asa'ib al-Haqq, the Houthis, Hamas, and numerous other terrorist organizations.

Reasons
Jihadism has an appeal for several reasons.

1) Base Islamic Architecture: Islam as a religion sets out many of the end-goals that the Jihadists are attempting to further. Islam as a religion supports the idea that there should be an Islamic government that rules according to Islamic Law. The religion supports the idea of martyrdom in war. The religion supports a traditional family structure. When the majority of Islamic Scholars condemn Islamic State or other Jihadist groups, they condemn the specific methods employed by these groups, but usually cannot condemn the ultimate project of creating an Islamic government that rules according to Islamic Law since this is part of the religion. Since Jihadists are promoting themselves based on this shared set of Islamic religious ideas, they have a leg up when convincing Muslims that their views are proper and moral.

Most Jihadists are also Salafists. A Salafist is someone who tries to recreate the Islam that existed at Muhammad's time, without the developments of religious jurisprudence during the Caliphal period (634-1923). There are tens of millions, if not hundreds of millions of Salafists, so the Salafist vision of Islam is relatively mainstream. It is worth noting that many Salafists are improperly called "Wahhabists" by their opponents, since Muhammad ibn Abd al-Wahhab was the founder of this movement.

2) Message & Results: Young Muslims want to join a movement that gives them meaning and has tangible results. Jihadists describe themselves as the only force that has managed to topple authoritarian governments, withstand the brutality of the West, and create an Islam that exactly as it had been practiced in Muhammad's time. While there are complex arguments which can undercut these assertions, they are, at least facially true.

3) Secular Authoritarianism: In much of the Islamic World, the Cold War period was defined by the presence of US-backed or USSR-backed secular dictators who strove against human rights and the only consistent opposition to these repressive governments were the Islamists (who believe that national laws should changed democratically to be based on the Shari'a or Islamic Law) and Jihadists.

4) Honest Grievances: The Jihadists give voice to particular Muslim grievances and seem honest about their anger in these regards. Most of the Middle East regimes have the resources to act on common Muslim grievances but dishonestly ignore their populations. Such grievances include: Israel's existence, US troops and bases throughout the Middle East, Russian bombings in the Middle East, etc. However, the Jihadists, as weak as they are, are actually trying to do something in this regard. That apparently honest venting of local grievances does not go unnoticed.

5) Pan-Islamic Unity: Jihadist groups argue that the only identity that matters for Muslims is the Muslim identity. National, ethnic, socially derived, interpersonal, work, and other identities are unimportant and should be relegated to the past. This very post-racial, post-ethnic view of personal identity is very attractive to Muslims who feel that they are subject to discrimination in their home countries.

6) Multiculturalism: There is a key difference between pluralism, which is the idea that a society should be colorblind and give people of all races and identities an equal shot, and multiculturalism, which is the idea that society should tolerate divergent cultural norms. Multiculturalism, especially in Western Europe, has resulted in Muslim-majority ghettos which focus around the idea of Muslim identity as opposed to citizenship within the larger Non-Muslim society. As they feel increasingly alienated from the larger society, they see themselves much more closely aligned with Jihadist groups who, similarly, make the Muslim identity their central identity.

7) Holiness: The most vile acts of Jihadist groups, like beheadings, corporal punishment, burning of enemies alive, throwing gays off of rooftops, etc. are in exact line with the penal code required under Islam. (Scholars will argue that the testimonial requirements are no satisfied, e.g. there is no appropriate trial, but the punishments are themselves legitimate.) By actually applying Islamic Law, the Jihadists show that they actually are following the religious precepts that they claim to be following.

One particularly harrowing story was that Jubhat an-Nusra (an offshoot of al-Qaeda Syria) videotaped several Islamic State fighters drinking Alcoholic Beverages and smoking cigarettes, where both actions are in violation of the Shari'a. Jubhat an-Nusra publicized this video to weaken Islamic State's claim to holiness. Upon seeing this footage, the Islamic State commanders immediately beheaded all of their fighters who were captured in the footage and destroyed any intoxicants in their possession. Following the law piously is part of their claim to legitimacy.